The Oñate treaty of 29 July 1617 was a secret treaty between the Austrian and Spanish branches of the House of Habsburg. The senior Habsburg branch of Spanish King Philip III reached an agreement with the junior Habsburg branch of Austrian Archduke Ferdinand II concerning allocation of key holdings still in dispute following the division of the House of Habsburg. Spanish Philip III agreed that Austrian Ferdinand II should be the only Habsburg to contend to be king of Bohemia and Hungary, allowing Ferdinand II to focus Austrian resources against estates in those two kingdoms who disputed the Habsburg right to inherit the titles from his childless cousin, Matthias of Habsburg, the reigning king and the Holy Roman Emperor. In turn, Ferdinand II granted Philip III undisputed reign of Habsburg territories along the "Spanish Road", a loosely connected string of Habsburg territories that ranged from Upper Italy, through Alsace and the Free County of Burgundy, to the Spanish Netherlands, securing the main Spanish supply route in the Eighty Years' War (or Dutch War of Independence) against the Protestant Dutch. The agreement was named after Iñigo de Oñate, the Spanish ambassador in Vienna, who negotiated its final version. Background In 1612, Rudolph II, Holy Roman Emperor, died and was succeeded by his brother Matthias. Since Matthias and the other archdukes of the main branch of the Austrian Habsburgs were childless, they agreed to transfer succession over their lands to the Styrian branch of the Habsburgs, thus effectively agreeing on the succession of Ferdinand II. The agreement amongst the Austrian Habsburgs was made without regard to King Philip III of Spain, head of the Spanish Habsburgs, who continued to press his own claims to Holy Roman succession on behalf of his sons. Philip's branch was more senior and more powerful than the Austrian branch of the Habsburgs, and Philip himself asserted a claim to the imperial crown as a grandson of Maximilian II and Charles V. The agreement to transfer succession to the Styrian Habsburgs concerned Holy Roman Emperor Matthias' chief political and religious advisor, Cardinal Melchior Klesl. As head of Matthias' Secret Council, Klesl was working to facilitate a reconciliation between Catholics and Protestants in Austria, hoping to prevent a continued paralysis of the Holy Roman Empire's institutions: the Reichstag was unable to convene in 1608 and 1613, and the common Türkenhilfe defense against the Ottoman threat was at risk. Cardinal